Cooking apparatus have heretofore been made with upper and lower cooking platens for two-sided cooking of food products such as hamburger patties. Two-sided cooking apparatus generally reduces the overall cooking time and amount of operator attention required for cooking the food products. However, there are a number of interrelated problems encountered in two-sided cooking apparatus, that are not presented in single surface grills.
The upper cooking platen in two-sided cooking apparatus for commercial food service establishments are generally large enough to enable cooking of a number of individual patties at the same time. The patties are preformed in several different nominal sizes and thicknesses and are commonly frozen for storage and transportation. The frozen patties are relatively rigid when initially placed on the lower cooking platen and if the upper platen rests only on the thickest patty or patties, even small differences in the initial thickness of the patties in the group being cooked could delay good heat transmitting contact between the upper platen and some of the thinner patties and result in uneven cooking of the patties. On the other hand, the patties soften and shrink or decrease in thickness as they thaw and cook. The weight of the upper cooking platen, if unrestrained or controlled, is such that it could excessively compress or compact the patties and adversely affect the final thickness, texture and appearance of the cooked patties. Thus, two-sided cooking apparatus presents several special problems including accommodating variations in initial thickness of the individual patties in the group being cooked; controlling the decrease in thickness of the patties that occurs during cooking; preventing excess compaction of the patties; and accommodating different groups of food products of nominally different thicknesses.
In order to control the spacing of the upper platen relative to the lower platen during cooking, prior clamshell grills have also been made with a plurality of upper platen stops adjustably mounted on the upper platen for engagement with the upper surface of the lower platen.
In U.S. Pat. No. 4,763,571, four stop pins are provided to extend to the cooking surface of the upper platen adjacent the corners and these pins had to be individually adjusted to change the platen spacing. U.S. Pat. No. 4,586,428 provided a single stop at the forward end of the platens support arm, and four individually adjustable stops for adjusting the vertical position of the upper platen relative to the support arm. U.S. Pat. No. 4,483,239 adjusted the pivot axis that supported the rear of the upper platen and provided a single stop at the front of the upper platen to control the spacing of the platens. U.S. Pat. No. 4,601,237 provides four cams that are interconnected for adjustment in pairs, to control the spacing between the platens. Each of the above required the adjustment of at least two and sometimes four adjustment devices in order to change the minimum spacing between the upper and lower cooking platens.
The upper platens in two-sided cooking apparatus are relatively heavy and present a problem of raising and lowering the upper platen at the beginning and end of a cooking cycle. U.S. Pat. Nos. 4,586,428 and 4,763,571 provide vertically movable counterweights to normally bias the upper platen to a raised condition and latch mechanism for holding the upper platen in a lowered condition. U.S. Pat. No. 4,483,239 provides a vertically arranged power cylinder with means for selectively actuating the power cylinders to raise and lower the upper platen. U.S. Pat. No. 4,165,682 provides a plurality of vertically disposed springs connected to the upper platen support arm at the rear of the cooking apparatus to aid in raising the upper platen.